In a metal-oxide-semiconductor field effect transistor (MOSFET), a gate electrode can be formed on a semiconductor substrate (insulated by a thin gate insulating layer) and a source/drain region can be formed on either side of the gate electrode. The MOS transistor can be controlled to form a channel region under the gate insulating layer by applying an appropriate bias voltage across the MOS transistor.
Attempts at improving the performance of semiconductor devices have been made by reducing the resistance of a cell by forming a silicide layer at an interface at which a contact will be formed and decreasing an interface resistance.
Other attempts have been made to increase the mobility of electrons or holes by applying a physical stress such as tensile stress or compressive stress and changing an energy band structure in a channel region.